When a switch changes its state the voltages and currents in connections made to the switch are changed and the changes can be sensed by suitable apparatus to determine the status of the switch. Errors can occur in areas of high electromagnetic noise when current or voltage changes may be induced in the connections which are sensed by the apparatus and give a false indication of the status of the switch. Such errors are particularly undesirable in water meters, as they would result in a consumer being over or undercharged.
Conventionally, because switch status sensors which count the number of pulses received from a switch-type water meter are subject to electromagnetic radiation, which can cause miscounting of switching events, the signals received from the switch are heavily filtered. However, this has the negative effect of slowing down the responsiveness, with the ultimate effect of missing real switch closures. The requirements for achieving fast response and electromagnetic noise immunity are irreconcilable using filtering alone.